1. Technical Field
This application relates to salts of compounds that inhibit protein kinase activity, and to compositions, formulations and methods related to U.S. Provisional Patent Application No. 60/892,373, filed Mar. 1, 2007, and U.S. Provisional Patent Application No. 60/911,789, filed Apr. 13, 2007.
2. Description of Related Art
Cancer (and other hyperproliferative diseases) is characterized by uncontrolled cell proliferation. This loss of the normal control of cell proliferation often appears to occur as the result of genetic damage to cell pathways that control progress through the cell cycle. The cell cycle consists of DNA synthesis (S phase), cell division or mitosis (M phase), and non-synthetic periods referred to as gap 1 (G1) and gap 2 (G2). The M-phase is composed of mitosis and cytokinesis (separation into two cells). All steps in the cell cycle are controlled by an orderly cascade of protein phosphorylation and several families of protein kinases are involved in carrying out these phosphorylation steps. In addition, the activity of many protein kinases increases in human tumors compared to normal tissue and this increased activity can be due to many factors, including increased levels of a kinase or changes in expression of co-activators or inhibitory proteins.
Cells have proteins that govern the transition from one phase of the cell cycle to another. For example, the cyclins are a family of proteins whose concentrations increase and decrease throughout the cell cycle. The cyclins turn on, at the appropriate time, different cyclin-dependent protein kinases (CDKs) that phosphorylate substrates essential for progression through the cell cycle. Activity of specific CDKs at specific times is essential for both initiation and coordinated progress through the cell cycle. For example, CDK1 is the most prominent cell cycle regulator that orchestrates M-phase activities. However, a number of other mitotic protein kinases that participate in M-phase have been identified, which include members of the polo, aurora, and NIMA (Never-In-Mitosis-A) families and kinases implicated in mitotic checkpoints, mitotic exit, and cytokinesis.
Aurora kinases are a family of oncogenic serine/threonine kinases that localize to the mitotic apparatus (centrosome, poles of the bipolar spindle, or midbody) and regulate completion of centrosome separation, bipolar spindle assembly and chromosome segregation. Three human homologs of aurora kinases have been identified (aurora-1, aurora-2 and aurora-3). They all share a highly conserved catalytic domain located in the carboxyl terminus, but their amino terminal extensions are of variable lengths with no sequence similarity. The human aurora kinases are expressed in proliferating cells and are also overexpressed in numerous tumor cell lines including breast, ovary, prostate, pancreas, and colon. Aurora-2 kinase acts as an oncogene and transforms both Rat1 fibroblasts and mouse NIH3T3 cells in vitro, and aurora-2 transforms NIH 3T3 cells grown as tumors in nude mice. Excess aurora-2 may drive cells to aneuploidy (abnormal numbers of chromosomes) by accelerating the loss of tumor suppressor genes and/or amplifying oncogenes, events known to contribute to cellular transformation. Cells with excess aurora-2 may escape mitotic check points, which in turn can activate proto-oncogenes inappropriately. Up-regulation of aurora-2 has been demonstrated in a number of pancreatic cancer cell lines. In additional, aurora-2 kinase antisense oligonucleotide treatment has been shown to cause cell cycle arrest and increased apoptosis. Therefore, aurora-2 kinase is an attractive target for rational design of novel small molecule inhibitors for the treatment of cancer and other conditions.
c-Kit, also known as CD117, is a well-studied proto-oncogene encoding an oncogenic receptor tyrosine kinase. (Yarden, Y. et al., “Human proto-oncogene c-Kit: a new cell surface receptor tyrosine kinase for an unidentified ligand,” Embo J 6:3341-51 (1987).) During receptor activation, the c-Kit ligand (stem cell factor, SCF or Steel factor) binds to the extracellular C2 immunoglobulin-like domains 1 through 3 of c-Kit and causes receptor homodimerization and trans-auto-phosphorylation which, in turn, leads to the activation of downstream signaling pathways and subsequent initiation of proliferation, survival, adhesion and chemotaxis, depending on environmental factors. (Blume-Jensen, P. et al., “Activation of the human c-Kit product by ligand-induced dimerization mediates circular actin reorganization and chemotaxis,” Embo J 10:4121-8 (1991).)
Activating or gain-of-function mutations in the c-Kit proto-oncogene have been identified in a variety of tumors including gastrointestinal stromal tumors (GIST). (Heinrich, M. C., Blanke, C. D., Druker, B. J. & Corless, C. L., “Inhibition of KIT tyrosine kinase activity: a novel molecular approach to the treatment of KIT-positive malignancies,” J Clin Oncol 20:1692-703 (2002); Hirota, S. et al., “Gain-of-function mutations of c-Kit in human gastrointestinal stromal tumors,” Science 279:577-80 (1998); Frost, M. J., Ferrao, P. T., Hughes, T. P. & Ashman, L. K., “Juxtamembrane mutant V560GKit is more sensitive to Imatinib (STI571) compared with wild-type c-Kit whereas the kinase domain mutant D816VKit is resistant,” Mol Cancer Ther 1:1115-24 (2002); Tian, Q., Frierson, H. F., Jr., Krystal, G. W. & Moskaluk, C. A., “Activating c-Kit gene mutations in human germ cell tumors,” Am J Pathol 154:1643-47 (1999).) In GIST, the resulting constitutive c-Kit tyrosine kinase activity provides growth and survival advantages, which are important in the pathogenesis of this disease. (Heinrich, M. C., Rubin, B. P., Longley, B. J. & Fletcher, J. A., “Biology and genetic aspects of gastrointestinal stromal tumors: KIT activation and cytogenetic alterations,” Hum Pathol 33:484-95 (2002).) c-Kit is validated as a critical target in GIST and while small molecule inhibitors can target c-Kit, such compounds are fraught with limitations. Imatinib mesylate, a potent inhibitor of c-Kit (Juurikivi, A. et al., “Inhibition of c-Kit tyrosine kinase by Imatinib mesylate induces apoptosis in mast cells in rheumatoid synovia: a potential approach to the treatment of arthritis,” Ann Rheum Dis 64:1126-31 (2005)) is currently approved for the treatment of GIST. However, in some cases where c-Kit is known to be upregulated, imatinib has been shown to be ineffective (Alexis, J. B., Martinez, A. E. & Lutzky, J., “An immunohistochemical evaluation of c-Kit (CD-117) expression in malignant melanoma, and results of Imatinib mesylate (Gleevec) therapy in three patients,” Melanoma Res 15:283-5 (2005)), possibly due to its inability to act against mutant forms of the c-Kit protein (Foster, R., Griffith, R., Ferrao, P. & Ashman, L., “Molecular basis of the constitutive activity and STI571 resistance of Asp816Val mutant KIT receptor tyrosine kinase,” J Mol Graph Model 23:139-52 (2004); Growney, J. D. et al., “Activation mutations of human c-Kit resistant to Imatinib are sensitive to the tyrosine kinase inhibitor PKC412,” Blood (2005); Gotlib, J. et al., “Activity of the tyrosine kinase inhibitor PKC412 in a patient with mast cell leukemia with the D816V KIT mutation,” Blood (2005); Corbin, A. S. et al., “In vitro and in vivo activity of ATP-based kinase inhibitors AP23464 and AP23848 against activation-loop mutants of Kit,” Blood 106:227-34 (2005)). To address this resistance, novel c-Kit inhibitors, with binding modes distinct from that of imatinib, might prove useful against mutant forms of the receptor.
PDGFRα is expressed in a wide variety of tissues, including kidney, testis, skin, intestine and lung epithelia, as well as in premature bone and muscle (Alvarez, R. H. et al., “Biology of platelet-derived growth factor and its involvement in disease,” Genetics in Clinical Practice 81:1241-57 (2006)). It is a very common signaling molecule at all stages of development and is involved in the regulation of differentiation and proliferation, as many proliferative genes are (Alvarez et al., supra). However, the continued expression of this receptor in various epithelial and mesenchymal cells suggests that it is also involved in the maintenance and regeneration of these tissues (Alvarez et al., supra). Activation of this receptor leads to stimulation of PI-3K, Ras-MAPK, and PLC signaling cascades leading to growth, actin cytoskeleton rearrangements, and chemotaxis (Alvarez et al., supra). A subset of invasive gastric carcinomas (including some gastrointestinal stromal tumors, GISTs), pancreas cancer, gliomas and astrocytomas are associated with PDGFR dysregulation. A subset of GIST tumors have been shown to have mutations in PDGFRα, occurring in either exon 18 (5.6%) or exon 12 (1.2%) (Alvarez et al., supra). The most common mutation occurring in exon (Giorgi, U. D. et al., “Imatinib and gastrointestinal stromal tumors: Where do we go from here?,” Mol Cancer Ther 4:495-501 (2005)) is the point mutation D842V and in exon 12 it is the point mutation V561D (Corless, C. L. et al., “PDGFRA mutations in gastrointestinal stromal tumors: frequency, spectrum and in vitro sensitivity to Imatinib,” J Clin Onco 23:5357-5364 (2005); Giorgi et al., supra). Both are activating mutations in vitro and interestingly, GIST tumors expressing mutated PDGFRα have not been shown to express mutant c-Kit (Alvarez et al., supra; Corless et al., supra; Giorgi et al., supra). The D842V mutant PDGFRα has been correlated with resistance to imatinib treatment. Based on these data, compounds that inhibit the D842V PDGFRα mutant may have activity in these resistant forms of GIST (Corless et al., supra).
Similar to c-Kit and PDGFR, Flt3 (Fms-like tyrosine kinase 3, FLk-2, or STK-1) is a member of the class III receptor tyrosine kinase family. Flt3 expression is seen predominantly in early CD34+ hematopoietic progenitor cells (Advani, A. S., “FLT3 and acute myelogenous leukemia: biology, clinical significance and therapeutic applications,” Cur Pharm Des 11:3449-57 (2005); Schmidt-Arras, D. et al., “Flt3 receptor tyrosine kinase as a drug target in leukemia,” Cur Pharm Des 10:1867-83 (2004)). The ligand for Flt3, Flt3 ligand (FL), is expressed in bone marrow stromal cells in either membrane-bound or soluble forms (Advani, supra; Schmidt-Arras et al., supra). Activation of Flt3 by FL initiates signal cascades that are essential in the proliferation, differentiation, and survival of normal hematopoietic progenitor cells (Advani, supra; Schmidt-Arras et al., supra). Two key downstream effectors of Flt3, PI-3K and Ras, initiate signaling cascades that stimulate cellular proliferation and cell survival (Advani, supra; Schmidt-Arras et al., supra). Mutations of Flt3 that over-express or constitutively activate the kinase, cause dysregulation of these downstream signaling cascades and may lead to leukemia. The most commonly identified mutations in AML are internal tandem duplications (ITD) of the juxtamembrane domain and point mutations of Asp835 (Advani, supra). Substitution of Asp835 with tyrosine, valine, histidine, glutamic acid, and aspargine have all been described with the D835Y substitution being the most common (Advani, supra; Schmidt-Arras et al., supra). Point mutations at D835 occur in the activation loop of the tyrosine kinase domain and cause the kinase to adapt an active configuration in the absence of ligand stimulation (Advani, supra). The prevalence of point mutations at D835 is: 7% in AML, 3% in MDS, and 3% in ALL (Schmidt-Arras et al., supra).
DNA repair pathways initiated in response to DNA damage utilize a protein called RAD51 which has been shown to be critical to the repair process in non-cancerous cells, but can be used as a mechanism of resistance to DNA-damaging agents in tumor cells. A correlation between the expression of high levels of RAD51 and resistance to chemotherapeutic drugs has been reported (Qiao, G-B, et al., “High-level expression of RAD51 is an independent prognostic marker of survival in non-small-cell lung cancer patients,” Brit J Cancer 93:137-43 (2005); Hansen, L. T. et al., “The role of RAD51 in Etoposide (VP16) resistance in small cell lung cancer,” Int J Cancer 105:472-79 (2003); Henning, W. et al., “Homologous recombination and cell cycle checkpoints: RAD51 in tumour progression and therapy resistance,” Toxicology 193:91-109 (2003)). Additionally, decreasing levels of RAD51 in cells increases their sensitivity to ionizing radiation (IR).
MP470 (4-[1]benzofuro[3,2-d]pyrimidin-4-yl-N-(1,3-benzodioxol-5-ylmethyl)piperazine-1-carbothioamide hydrochloride) (e.g., WO2005/037825) has demonstrated inhibitory activity against multiple protein kinases, including Aurora kinase, c-kit kinase and PDGFRα. In light of its potent anticancer activity, there is a need for identifying effective formulations of MP470 for clinical use. There is also a need for identifying other therapies or treatment modalities that can be effectively used in combination with formulations comprising MP470. The present invention addresses these needs and offers other related advantages.